|  | 2.1 | Various LAN Communication Problems
| 2.1.6 | Ethernet 10BASE-T transmission time

All networks have what is called a "bit time" or a "slot time". Many LAN technologies, such as Ethernet, define a bit time as the basic unit of time in which ONE bit can be sent. In order for the electronic or optical devices to recognize a binary one or a binary zero, there must be some minimum duration during which the bit is "on" or "off". Transmission time equals the number of bits being sent times the bit time for a given technology. Another way to think about transmission time is as the time it takes a frame to actually be transmitted (small frames take a shorter amount of time, large frames take a longer amount of time to be transmitted). The table shows the transmission times for four different 10BASE-T frame sizes. Each 10 Mbps Ethernet bit has a 100 ns window for transmitting (the bit time). A byte equals 8 bits. Therfore, 1 byte takes a minimum of 800 ns to transmit. A 64-byte frame (the smallest allowable 10BASE-T frame, so that CSMA/CD will work properly) takes 51, 200 ns, or 51.2 microseconds, to transmit (64 bytes at 800 ns per byte equals 51, 200 ns and 51, 200 ns divided by 1000 equals 51.2 microseconds). Transmission time of an entire 1000-byte frame from the source station requires 800 microseconds just to complete the frame. The time at which the frame actually arrives at the destination station depends on the additional latency (delay) introduced by the network. This latency can is due to NIC delays, propagation delays, and layer 1, 2, or 3 device delays.
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